An outer sleeve for a double walled cup and a process for manufacturing same The present invention relates to an outer sleeve for a double walled cup, which is formed from a blank made of paper material and which is provided with an inwardly rolled curled part, whereby the blank is joined to form a tube shape by means of an overlap of two longitudinal edges of the blank.
The present invention relates further to a process for manufacturing such outer sleeves.
Outer sleeves of the above mentioned type are applied in large numbers in manufacturing in order to improve the insulating properties of paper cups. By applying the outer sleeve to a cup made of paper material, a double-walled insulating cup having an essentially ring-shaped hollow space between the inner sleeve and the outer sleeve of the cup is formed, which lends the cup good insulating properties. In order to ensure a sufficiently large gap between the inner sleeve and the outer sleeve, it is common practice to apply at least one inwardly rolled curled part on the outer sleeve. This curled part can be designed in a variety of ways.
In the manufacture of the outer sleeve, a flat-lying blank made of a paper material is joined by means of overlapping two longitudinal edges of the blanks. An inwardly rolled curled part is then applied to the so formed outer sleeve. The pre-manufactured outer sleeve is subsequently slid in axial direction onto the also pre-manufactured cup and attached thereto. A double-walled cup is thus formed.
It can happen that the outer sleeve with the inwardly rolled curled part catches on the skirt of the inner cup when the outer sleeve is slid axially onto the inner cup sleeve.
It is an object of the present invention to create an outer sleeve for a double-walled cup which does not easily catch on the inner cup when slid on.
This object has been achieved in that the curled part is glued or sealed onto the inside of the outer sleeve at least in the area of the overlap.
Because of the enlarged thickness of the outer sleeve in the area of the overlap, the resilient properties are particularly strong in this area. In the case of relatively stiff paper material, the inwardly rolled curled part at the outer sleeve in the area of the overlap is not formed exactly, but rather has the tendency to unroll because of the stiffness of the paper material. The inner diameter of the outer sleeve within the curled part is as a result reduced in the area of the overlap and can lead to catching of the outer sleeve on the skirt of the inner cup when the outer sleeve is axially slid onto the inner cup. Gluing or sealing of the curled part in the area of the overlap effectively prevents the curled part from partly unrolling again. The catching of the outer sleeve when being slid onto the inner cup due to an insufficiently clear inner diameter in the area of the curled part can be effectively prevented.
Gluing or sealing of the curled part on the inside of the outer sleeve is particularly advantageous when the curled part comprises an area extending parallel to the outer sleeve, in which the material of the curled part lies plane with the inner side of the outer sleeve.
A non-coated paper material is frequently used for the outer sleeve, as the outer sleeve does not come into contact with the liquid which is poured into the cup. In the application of a non-coated paper material, a stripe of glue is applied to the longitudinal edge of the blank before the blank is joined to a tube-shape. Various types of glue can be used. Suitable are for example cold glue, hot glue or in particular a hot-melt adhesive (“Hot-Melt”).
For certain applications it can be advantageous to manufacture the outer sleeve from a paper material which is coated on at least one side, for example a polyethylene coating. The curled part can be sealed on the inside of the outer sleeve by means of heating the synthetic coating. Sealing or gluing of the curled part can also be carried out circumferentially along the entire circumference of the outer sleeve.
For the efficient manufacture of the outer sleeve it is advantageous when the blank comprises a recess on a longitudinal edge which recess comes to lie in the area of the overlap. The recess is so designed that in the overlapping of the two longitudinal edges, a section of the stripe of glue is not covered. When forming the inwardly curled part, the uncovered section of the stripe of glue serves to glue the curled part in the area of the overlap inside on the outer sleeve.
The recess of the blank in the area of the overlap is advantageously so designed that the curled part in an area of the overlap leads to an overall thickness of the outer sleeve which corresponds approximately to three times the material thickness of the blank. In contrast to a standard minimum of four times the material thickness in the area of the overlap, the overall reduced thickness in the area of the overlap also reduces the risk of the outer sleeve catching on the inner cup while being slid thereon.
The outer sleeve according to the present invention is particularly suitable for cups which have an essentially truncated cone shape. Accordingly, the outer sleeve can also be conically designed. The glued or sealed on curled part on the inside of the outer sleeve is hereby applied to that end of the outer sleeve which has the smaller circumference. An outer sleeve according to the present invention is however not just suitable for cups made of paper material, but rather can be applied as an outer sleeve for cups made of synthetic material.
Furthermore an outer sleeve according to the present invention is particularly suitable for an inner cup comprising a widening on its skirt, whereby a lower edge of the widening forms a standing base for the cup. In the case of inner cups having a widened skirt, the sliding on of an outer sleeve is particularly critical, as the diameter enclosing the widening can be as large or even larger than the inner diameter of the curled part of the outer sleeve. Even in the case of such inner cups, an outer sleeve according to the present invention can effectively prevent the outer sleeve catching when being axially slid on to the inner cup.